Born Cassius Clay in Louisville, Kentucky on January 17, 1942. He began training as a boxer when he was 12 years old. Ali began winning important amateur heavyweight boxing matches in 1960, including an Olympic gold medal. He turned professional and won the national heavyweight championship in 1964 by defeating Sonny Liston. Clay converted to Islam in 1967 and took the name, Muhammad Ali.
He was known for the style he brought to boxing, as well as the amusingly cocky poetry he would recite during interviews. One of his famous verses predicted that he would "float like a butterfly, sting like a bee" and knock out Sonny Liston in "round eight to prove I'm great." Ali became a controversial figure when he refused to enter US military service. He was stripped of his title, but began a comeback in 1970, fighting against such opponents as Joe Frazier and George Foreman. Ali succeeded in winning the national title, losing it, and regaining it. Ali retired from boxing in 1981 a the age of 39. He was diagnosed with Parkinson Disease in 1984 and suffered from it the rest of his life.